One of the big reasons Raimi wanted to do 'Oz 'is so that he could work with Robert Downey Jr., who's still in negotiations to take on the role of the Wizard (fingers crossed those negotiations end with Downey Jr. in the part). Raimi is better known nowadays for his work on the 'Spider-Man' movies, however the Raimi that sticks in my mind is the one responsible for the 'Evil Dead' franchise and the gory, gruesome images that resulted (he later turned the franchise into a parody of itself with 'Army of Darkness').
While 'The Wizard of Oz' is mostly known for being cute, a modern turn would likely be more twisted as with the recent 'Alice In Wonderland' movie, which was made by the same studio behind this 'Oz' movie, Disney.
Other directors could have handled the franchise with a similar style. Terry Gilliam, Tim Burton (who directed the aforementioned 'Alice In Wonderland') or even Guillermo del Toro are all known for their unique visual styles, and any of them could easily have made a memorable Oz movie. Could this become Sam Raimi's next great franchise, or is he taking this just to pass the time before World of Warcraft destroys movie theaters everywhere?